An ultrasonic diagnosis apparatus is a diagnosis apparatus to display images of in vivo information. The ultrasonic diagnosis apparatus is used as a useful apparatus for noninvasive observation in real time at low cost without exposure to radiation as compared with other image diagnosis apparatuses such as an X-ray diagnosis apparatus and an X-ray computed tomography apparatus. The ultrasonic diagnosis apparatus has a wide range of applications including diagnosis of circulatory organs such as the heart, abdominal organs such as the liver and kidney, and peripheral vessels, diagnosis in obstetrics and gynecology, and diagnosis of breast cancer.
In general, the ultrasonic diagnosis apparatus obtains one-dimensional vital information by a one-time pulse transmitted from a probe. Repeatedly performing such transmission/reception while changing the transmitting direction can reconstruct a two-dimensional tomogram. This image represents the form of an organ or the like in an object and is called a B-mode image or simply called a tomogram, which is a most basic picture mode for ultrasonic diagnosis.
Likewise, repeatedly performing transmission/reception in three-dimensional directions can obtain three-dimensional information of a living body organ. Currently, visualization of three-dimensional information using ultrasonic waves has already been clinically used owing to a technique of three-dimensionally changing the transmitting/receiving direction by mechanically swinging the probe or electronically controlling the delays of a plurality of transducers two-dimensionally arrayed.
Using three-dimensional information can perform image reconstruction which cannot be performed by using a simple tomogram like a conventional B-mode image. This makes it possible to improve the efficiency of diagnosis and provide new diagnosis information. For fetal observation, for example, tomographic observation of a fetus is the mainstream technique in the normal B mode. In contrast, using three-dimensional information makes it possible to reconstruct an image of the face of a fetus such that the surface of the face looks as if it were imaged by a camera.
It is not always possible to implement a three-dimensional image like that described in the case of the fetus in all cases. In the case of a fetus, amniotic fluid exists between the surface of the fetus and the probe. The amniotic fluid generally includes no ultrasonic echo, and hence the surface of an object of interest can be imaged relatively easily. This applies to the inner walls of the heart, blood vessels, and bile ducts. Since a blood portion in a cardiac chamber or the like includes no echo, it is easy to visualize the surface of the blood portion.
In other cases, however, it is not easy to observe surfaces with ultrasonic waves. Assume that the state of the surface of a tumor in the liver is to be imaged. In this case, solid echo signals also exist outside the tumor. For this reason, in order to observe the surface of the tumor, it is necessary to carefully remove signals outside the tumor.
The observation of the surface of the liver has attracted attention. In some cases, the tissue properties of the liver diffusedly change from the onset of hepatitis up to hepatic cirrhosis. However, a characteristic of hepatitis also appears on the liver surface. That is, the surface becomes uneven. Currently, such a state is optically observed with an abdominal endoscope. This technique is to observe the surface of an abdominal region of a patient by inserting an endoscope (camera) into a small hole formed in the abdominal region of the patient under anesthesia. Since an air gap is generally provided between the liver and the peritoneum, such optical observation can be done.
If, however, an image of the liver surface like that described above is to be obtained by an ultrasonic diagnosis apparatus, since the liver surface is in contact with the peritoneum, it is difficult to image the liver surface by using general three-dimensional ultrasonic waves as in the case of the tumor surface described above.